Field
The present invention relates to an AC-driven LED lighting apparatus using a multi-cell LED. More particularly, the present invention relates to an AC-driven LED lighting apparatus using a multi-cell LED, in which the multi-cell LED is configured to allow a plurality of light emitting cells included in the multi-cell LED to be independently controlled and the light emitting cells in the multi-cell LED can be sequentially driven under control of an LED driving module.
Description of the Background
Generally, a light emitting diode (LED) can be driven only by DC power due to inherent characteristics thereof. As a result, a lighting apparatus employing such a conventional LED is limited in applicability and requires a separate circuit such as an SMPS when used in domestic settings employing AC power, thereby complicating circuit design of a lighting apparatus while increasing manufacturing costs
To solve such problems, various studies have focused on development of an AC-driven LED lighting apparatus which can be driven by AC power.
FIG. 1 is a block diagram of a conventional AC-driven LED lighting apparatus using LEDs and FIG. 2 is a waveform diagram of rectified voltage and LED drive current of the conventional AC-driven LED lighting apparatus shown in FIG. 1.
As shown in FIG. 1, the conventional AC-driven LED lighting apparatus may include an LED light emitting module composed of a plurality of LEDs 20 and an LED driving module 10. The LED driving module 10 supplies a rectified voltage Vrec to the LED light emitting module through full-wave rectification of AC voltage received from an AC power source, and is configured to control sequential driving of a first LED group 30, a second LED group 40, a third LED group 50 and a fourth LED group 60, which constitute the LED light emitting module, according to a volume level of the rectified voltage Vrec.
In addition, the LED light emitting module is composed of the first LED group 30, the second LED group 40, the third LED group 50 and the fourth LED group 60, each of which includes a plurality of LEDs 20, in which the first to fourth LED groups 30 to 60 are sequentially driven by control of the LED driving module 10. Here, the LEDs 20 constituting each of the LED groups are typical LEDs and configured to be entirely turned on or off regardless of whether the LEDs are single-cell LEDs each including a single cell therein or MJL LEDs each including a plurality of cells therein.
Referring to FIG. 2, in operation of the conventional AC LED lighting apparatus as described above, the LED driving module 10 determines the voltage level of the rectified voltage Vrec and sequentially drives the first LED group 30, the second LED group 40, the third LED group 50 and the fourth LED group 60 according to the determined voltage level of the rectified voltage Vrec.
Accordingly, the LED driving module 10 controls only the first LED group 30 to be turned on, when the voltage level of the rectified voltage Vrec reaches a first forward voltage level Vf1.
In addition, when the voltage level of the rectified voltage Vrec is increased and reaches a second forward voltage level Vf2, the LED driving module 10 controls only the first LED group 30 and the second LED group 40 to be turned on.
Further, when the voltage level of the rectified voltage Vrec is increased and reaches a third forward voltage level Vf3, the LED driving module 10 controls the first LED group 30, the second LED group 40 and the third LED group 50 to be turned on, and similarly, when the voltage level of the rectified voltage Vrec reaches a fourth forward voltage level Vf4, the LED driving module 10 controls all of the first to fourth LED groups 30 to 60 to be turned on.
Likewise, when the voltage level of the rectified voltage Vrec is decreased to less than the fourth forward voltage level Vf4 after reaching a peak voltage level, the LED driving module 10 turns off the fourth LED group 60. Then, when the voltage level of the rectified voltage Vrec is decreased to less than the third forward voltage level Vf3, the LED driving module 10 turns off the third LED group 50; when the voltage level of the rectified voltage Vrec is decreased to less than the second forward voltage level Vf2, the LED driving module 10 turns off the second LED group 40; and when the voltage level of the rectified voltage Vrec is decreased to less than the first forward voltage level Vf1, the LED driving module 10 turns off the first LED group 30.
Since the first to fourth LED groups 30 to 60 are sequentially driven, such a conventional AC-driven LED lighting apparatus suffers brightness deviation according to locations of the LED groups. Moreover, in the conventional AC-driven LED lighting apparatus, the LEDs 20 of the first to fourth LED groups 30 to 60 are driven in different sections according to the LED groups to which the corresponding LEDs 20 pertain, thereby causing deviation in luminous flux and on/off-period between the LEDs 20.